The disclosure relates to an axial piston machine.
Axial piston machines have a cylinder drum, on the circumference of which a plurality of cylinder bores are provided in a uniformly distributed manner, said cylinder bores being introduced in the axial direction and being intended for the respective pistons, and a drive shaft which is connected to the cylinder drum for rotation therewith. Axial piston machines of oblique-axis construction and of swashplate construction are known. In the case of the last-mentioned construction, the cylinder drum is arranged concentrically with respect to the drive shaft, and both rotate about a common longitudinal axis. In each cylinder bore, a piston is accommodated in a displaceable manner and is connected at its respective end portion remote from the cylinder drum in an articulated manner to a sliding block which, during the operation of the axial piston machine, revolves about the longitudinal axis and, in the process, slides along a swashplate.
In order to produce the stroke of the pistons, the swashplate is positioned obliquely with respect to the longitudinal axis. In the case of an adjustable axial piston machine of swashplate construction, the swashplate is pivotable, as a result of which the stroke of the pistons in the cylinder bores is adjusted. Therefore, during the pump mode, the delivery volume flow of the pressure medium can be adjusted, or, during the motor mode, the rotational speed of the drive shaft serving as the output shaft can be adjusted.
The cylinder bores of the cylinder drum have to be connected once to the high-pressure side and once to the low-pressure side of the axial piston machine during a revolution. For this purpose, the rotating end surface of the cylinder drum that is spaced apart from the swashplate and in which the orifices of the cylinder bores are arranged is tensioned in the axial direction against a stationary distributor plate, which is also referred to as a control plate or distributor disk or control disk. Said distributor plate has a circular-arc-shaped high-pressure kidney-shaped aperture and a circular-arc-shaped low-pressure kidney-shaped aperture. Axial piston machines in which the two kidney-shaped apertures can be operated as a high-pressure kidney-shaped aperture and as a low-pressure kidney-shaped aperture according to choice are also known.
In order to minimize wear and friction, a hydrostatic relief is known which is arranged between the cylinder drum and the distributor plate in or on the contact surfaces thereof.
In the case of an axial piston machine in the pump mode, operationally induced contact pressure forces are higher than in the case of an axial piston machine in the motor mode.
Document DE 10 2010 006 895 A1 presents an axial piston machine with a hydrostatic main relief field and with a hydrostatic additional relief field on the distributor plate, which additional relief field can be switched on or off depending on the type of operation. Furthermore, a second virtually “mirrored” additional relief field is proposed on the other side of the distributor plate if the axial piston machine concerned also permits a pressure side change of the two kidney-shaped apertures.
A disadvantage of axial piston machines of this type is that, by means of various forces and moments which arise at the cylinder drum during the operation of the axial piston machine, the cylinder drum may lift off on one side and therefore easily tilt in the direction of or over a tilting point. This tilting point lies on the distributor plate in the high-pressure-side quadrant of the distributor plate, which quadrant is defined by the first part of the stroke movement of the pistons of the axial piston machine in the pump mode. This results in undesirable leakage which reduces the volumetric efficiency of the axial piston machine.
Furthermore, it is known from the prior art to distribute a plurality of segments uniformly at the edge of the cylinder drum, said segments being designed (not as hydrostatic relief fields) to counteract tilting of the cylinder drum and result in an increase in the diameter of the cylinder drum, as a result of which the tilting point is displaced radially outward. The risk of tilting over the tilting point of the first quadrant of the distributor plate is significantly reduced as a result.
A disadvantage of axial piston machines of this type is that the multiplicity of segments is expensive to manufacture and, because of their structural design, the segments increase the wear and the friction loss between the cylinder drum and the distributor plate.